Display notification where no map data is available and suggest how to get it.

[gefrierbrand]

As I first installed and started navit I thought it's not done loading and a bit later I though it's not working correctly as all I could see was this annoing pale orange background.

I quickly figured it out that no default maps were installed but I had to constult the Wiki, tweak the config file and so on.

This is very repelling to new and not-so-tech-related users.

I'd like to see some kind of notification which prints something like "no map data available here" as you can sometimes come across on google maps et.al.

This might also feature a link to the osm map extractor featuring somethig like "click here tho get maps of his area"

A system like this would not only help new users but also would make it easier to indicate where the maps in your mapset end and which regions you might want to add etc.